"Starhopper completed tethered hop. All systems green."

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For a couple of weeks, SpaceX engineers and technicians have been conducting a series of tests on its Starship prototype vehicle in South Texas. For example, they have loaded liquid oxygen and liquid methane fuels onto the vehicle, studied the cryogenic properties of the fuel tanks, and then removed the propellant.

As expected, this was all a little dull for those eager to see Starhopper light its single Raptor engine—until Wednesday evening. Shortly after night fell over the southern Texas test facility, Starhopper roared to life for the first time, firing its Raptor engine and lifting briefly off the pad. The vehicle did not go far, because for now it remains solidly tethered to the ground.

This represents the first phase of tests for the Starship vehicle. The prototype built in South Texas, near Brownsville, is not a particularly high-fidelity mock-up, but it is needed to test how a vehicle designed to land propulsively on other worlds, and take off, handles such conditions. These minute hops will progressively become larger as SpaceX adds two more Raptor engines to Starhopper in the coming months.

It is not known how high Starhopper will eventually climb during these tests. Back in 2012 and 2013, when SpaceX was testing its Grasshopper vehicle to prove out technologies for landing its Falcon 9 rocket, the vehicle climbed as high as 744 meters during its flight campaign.

The work on Starhopper continues as SpaceX prepares to test-fire another rocket—the Falcon Heavy booster. The window for a static fire test opens at 6pm ET Thursday, and closes at midnight. Provided this test firing of all of the vehicle's 27 engines is successful, the Arabsat-6A launch may occur as early as Sunday, April 7, at 6:36pm ET. This will be only the Falcon Heavy rocket's second flight.

231 Reader Comments

Can anyone enlighten me on how far down the Raptor can throttle - does StarHopper have to slam like the Falcon 9 or can it hover like the New Shepard?

The point of the slam is fuel consumption - longer landing burns require more fuel. By doing a 'slam' the Falcon 9 minimizes the amount of fuel it needs to carry for the rest of the flight. (And increases the amount of payload it can lift.)

From what I've seen, I'm pretty sure the Falcon 9 can hover if they want it to - but there's no good reason to.

No, the F9 cannot hover and has to slam to land at all. When landing, one engine has enough thrust to send the whole (mostly empty) vehicle back up again. So to land, it has to match the cusp of its speed with the cusp of the landing pad. Easy for a computer - "match these curves" - but hard for a human pilot.

A F9 can hover if it has >30t of prop in the tanks. You wouldn't want to do that. Even if you had excess prop is makes sense to burn it down prior to MECO in order to give the upper stage the largest margin possible. I mean anything can however given the right mass to weight ratio. There just is no reason to do so.

That's true. In a realistic operational regime, it's too light to hover. With a bunch of ballast, well, as you say...

Hopper should be able to hover, as it's a bigger heavier ship already. Hopper hover examples might look like early New Shepard hovers, where it zeroes out its vertical speed above the pad before coming in for a dainty kiss landing.

Considering the Merlins are the significantly less-efficient gas-generator cycle engines, the Raptor has been something I've been looking forward to for a long time. Finally, an American-made full-cycle engine. I know it's been test-fired, but I am psyched to see it used in a test on a vehicle and looking forward to seeing it fly! Kudos once again to Musk and the SpaceX team.

Forget "American-made," this is the first Full Flow Staged Combustion engine actually mounted on a vehicle, ever, by anyone. And possibly only the second one to ever be test-fired in full FFSC mode (not counting the small-scale Raptors as separate engines).

Not to mention first large scale use AFAIK of autogenous pressurization. Kiss all those helium valve and COPV problems good bye.

Titan II used autogenous pressurization as one of the major changes from Titan I.

Titan II used hypergols - non-cryogenics. Did they have a gas generator that burned oxidizer rich to pressurize the oxidizer tank and a gas generator that burned fuel rich to pressurize the fuel tank?

You don't need a preburner which is rich in the appropriate propellant. Using heat exchangers you can use hot fuel rich gas to heat up cryogenic oxidizer. The STS SSME used cryogenic hydrogen and oxygen but the preburner for both pumps has fuel rich. The STS used auto pressurization for both propellants in the external fuel tank.

True that the astronauts may feel more g load during other parts of the descent depending on where the Starship is coming from, (LEO vs return from the Moon). In any case, that's a ride I would love to take if I were a few years younger.

Can anyone enlighten me on how far down the Raptor can throttle - does StarHopper have to slam like the Falcon 9 or can it hover like the New Shepard?

The point of the slam is fuel consumption - longer landing burns require more fuel. By doing a 'slam' the Falcon 9 minimizes the amount of fuel it needs to carry for the rest of the flight. (And increases the amount of payload it can lift.)

From what I've seen, I'm pretty sure the Falcon 9 can hover if they want it to - but there's no good reason to.

No, the F9 cannot hover and has to slam to land at all. When landing, one engine has enough thrust to send the whole (mostly empty) vehicle back up again. So to land, it has to match the cusp of its speed with the cusp of the landing pad. Easy for a computer - "match these curves" - but hard for a human pilot.

A F9 can hover if it has >30t of prop in the tanks. You wouldn't want to do that. Even if you had excess prop is makes sense to burn it down prior to MECO in order to give the upper stage the largest margin possible. I mean anything can however given the right mass to weight ratio. There just is no reason to do so.

You might have Super Heavy hover briefly to align itself with the launch clamps, and New Glenn might hover so they can get a better margin of error early on before refining it down to a hoverslam.

Just a note - this video isn't from SpaceX. It was recorded by "BocaChicaGal" a local resident who for months has posted daily photos and videos of SpaceX's hopper build and operations on NSF forums regardless of weather. On behalf of space enthusiasts everyone I would like to give her a huge and hearty thank you.

Considering the Merlins are the significantly less-efficient gas-generator cycle engines, the Raptor has been something I've been looking forward to for a long time. Finally, an American-made full-cycle engine. I know it's been test-fired, but I am psyched to see it used in a test on a vehicle and looking forward to seeing it fly! Kudos once again to Musk and the SpaceX team.

Forget "American-made," this is the first Full Flow Staged Combustion engine actually mounted on a vehicle, ever, by anyone. And possibly only the second one to ever be test-fired in full FFSC mode (not counting the small-scale Raptors as separate engines).

Not to mention first large scale use AFAIK of autogenous pressurization. Kiss all those helium valve and COPV problems good bye.

Titan II used autogenous pressurization as one of the major changes from Titan I.

Titan II used hypergols - non-cryogenics. Did they have a gas generator that burned oxidizer rich to pressurize the oxidizer tank and a gas generator that burned fuel rich to pressurize the fuel tank?

Typically heat exchangers are used to heat prop or oxidizer and that heated gas is then sent back into the tank to maintain pressure.

Considering the Merlins are the significantly less-efficient gas-generator cycle engines, the Raptor has been something I've been looking forward to for a long time. Finally, an American-made full-cycle engine. I know it's been test-fired, but I am psyched to see it used in a test on a vehicle and looking forward to seeing it fly! Kudos once again to Musk and the SpaceX team.

Forget "American-made," this is the first Full Flow Staged Combustion engine actually mounted on a vehicle, ever, by anyone. And possibly only the second one to ever be test-fired in full FFSC mode (not counting the small-scale Raptors as separate engines).

Not to mention first large scale use AFAIK of autogenous pressurization. Kiss all those helium valve and COPV problems good bye.

Titan II used autogenous pressurization as one of the major changes from Titan I.

Titan II used hypergols - non-cryogenics. Did they have a gas generator that burned oxidizer rich to pressurize the oxidizer tank and a gas generator that burned fuel rich to pressurize the fuel tank?

Typically heat exchangers are used to heat prop or oxidizer and that heated gas is then sent back into the tank to maintain pressure.

That is how it works with cryogenics but Titan II used room temp hypergols.

Just a note - this video isn't from SpaceX. It was recorded by "BocaChicaGal" a local resident who for months has posted daily photos and videos of SpaceX's hopper build and operations on NSF forums regardless of weather. On behalf of space enthusiasts everyone I would like to give her a huge and hearty thank you.

On that note ... some idiot recently over-flied not only right on top of the hopper and the facility, but also close enough to discern the faces of SpaceX staff.

This of course went over the line and now there is sign banning drones altogether in the area.Not that SpaceX is against photography of it`s operations at Boca Chica operations (it is not!), but one has to be responsible (and sane) enough.

It only took one. Now we all suffer the consequences. (Only ground-based photos)I in particular very much enjoyed the overflying over the construction site and the improvised launch pad. No more, unless someone get explicit permission straight from he source. (SpaceX)

"During flight, pressure was maintained by the engine autogenous pressurization system. The autogenous system generated pressure by extracting hot gas from the turbine housing of the turbine pump assembly. The hot gas was directed through a gas cooler (fig. 13) to cool the gas before it went to the fuel tank for pressurization. The oxidizer tank was pressurized by extracting oxidizer from the TPA, and routing the liquid oxidizer through a super heater where it was changed to a gas for the pressurization of the oxidizer tank."

My take is scaling it up will make it cheaper to operate in the long run. The bigger, fluffy, size makes reentry easier. LOX/methane is super cheap. Extra engines gives it redundancy, increasing odds of mission success. Designing it for low cost, fast turn-around is super smart. No one has ever really designed a reusable launch vehicle like this.

Considering the Merlins are the significantly less-efficient gas-generator cycle engines, the Raptor has been something I've been looking forward to for a long time. Finally, an American-made full-cycle engine. I know it's been test-fired, but I am psyched to see it used in a test on a vehicle and looking forward to seeing it fly! Kudos once again to Musk and the SpaceX team.

I think the Raptor is the first Full Flow Staged Combustion engine to fly. The only others built never flew. There are quite a few oxidizer rich and fuel rich staged combustion cycle engines that have flown though.

Just a note - this video isn't from SpaceX. It was recorded by "BocaChicaGal" a local resident who for months has posted daily photos and videos of SpaceX's hopper build and operations on NSF forums regardless of weather. On behalf of space enthusiasts everyone I would like to give her a huge and hearty thank you.

On that note ... some idiot recently over-flied not only right on top of the hopper and the facility, but also close enough to discern the faces of SpaceX staff.

This of course went over the line and now there is sign banning drones altogether in the area.Not that SpaceX is against photography of it`s operations at Boca Chica operations (it is not!), but one has to be responsible (and sane) enough.

It only took one. Now we all suffer the consequences. (Only ground-based photos)I in particular very much enjoyed the overflying over the construction site and the improvised launch pad. No more, unless someone get explicit permission straight from he source. (SpaceX)

Whoever did it should have the shit fined out of them. If you lose control and it comes crashing down it's probably not a risk to hopper depending on the size of the drone but you can kill a person quite easily. People never think about this when they overfly crowds and it's expressly forbidden by the FAA. We use drones at work, and it is no joke on following the rules.

Just a note - this video isn't from SpaceX. It was recorded by "BocaChicaGal" a local resident who for months has posted daily photos and videos of SpaceX's hopper build and operations on NSF forums regardless of weather. On behalf of space enthusiasts everyone I would like to give her a huge and hearty thank you.

Wouldn't that be a "Laurel and Hardy" thank you? (credit to Mel Brooks and "Blazing Saddles")

Isn't that one of the internet requirements? If a discussion goes on long enough, there will be a reference to Monty Python or Mel Brooks?

A nice (coincidental) FU to Boeing on the day news comes out on yet another slip in their better funded manned program. Space X is moving on while they‘re stuck.

Small teams go so much faster. I remember when SpaceShipOne had a stability problem. Rutan mounted part of the tail on the back of a pickup and drove it down the runway to collect data. BA or NG will spend months building and verifying a computer simulation.

Just a note - this video isn't from SpaceX. It was recorded by "BocaChicaGal" a local resident who for months has posted daily photos and videos of SpaceX's hopper build and operations on NSF forums regardless of weather. On behalf of space enthusiasts everyone I would like to give her a huge and hearty thank you.

Wouldn't that be a "Laurel and Hardy" thank you? (credit to Mel Brooks and "Blazing Saddles")

Isn't that one of the internet requirements? If a discussion goes on long enough, there will be a reference to Monty Python or Mel Brooks?

That's a laurel and hearty handshake, thankyouverymuch.

And if the discussion goes on long enough there will be ponies. Rocket ponies.

Just a note - this video isn't from SpaceX. It was recorded by "BocaChicaGal" a local resident who for months has posted daily photos and videos of SpaceX's hopper build and operations on NSF forums regardless of weather. On behalf of space enthusiasts everyone I would like to give her a huge and hearty thank you.

On that note ... some idiot recently over-flied not only right on top of the hopper and the facility, but also close enough to discern the faces of SpaceX staff.

This of course went over the line and now there is sign banning drones altogether in the area.Not that SpaceX is against photography of it`s operations at Boca Chica operations (it is not!), but one has to be responsible (and sane) enough.

It only took one. Now we all suffer the consequences. (Only ground-based photos)I in particular very much enjoyed the overflying over the construction site and the improvised launch pad. No more, unless someone get explicit permission straight from he source. (SpaceX)

Whoever did it should have the shit fined out of them. If you lose control and it comes crashing down it's probably not a risk to hopper depending on the size of the drone but you can kill a person quite easily. People never think about this when they overfly crowds and it's expressly forbidden by the FAA. We use drones at work, and it is no joke on following the rules.

Yeah it only takes one idiot to get the rules changed to the detriment of everyone else. There was a fellow who took really good quality videos and always flew his drone outside SpaceX's property line but he is grounded too.

Considering the Merlins are the significantly less-efficient gas-generator cycle engines, the Raptor has been something I've been looking forward to for a long time. Finally, an American-made full-cycle engine. I know it's been test-fired, but I am psyched to see it used in a test on a vehicle and looking forward to seeing it fly! Kudos once again to Musk and the SpaceX team.

I think the Raptor is the first Full Flow Staged Combustion engine to fly. The only others built never flew. There are quite a few oxidizer rich and fuel rich staged combustion cycle engines that have flown though.

The RD-270M would have been interesting. Full Flow Staged Combustion with N2O4/pentaborane to get 365 seconds of vacuum Isp and 1.6 million pounds of thrust.

Grasshopper tests were really only 6~7 years ago? Wow, today, these propulsive landings have become the normal for SpaceX, just goes to show how fast they actually move.

Can you imagine any of the other traditional space companies trying this?

Boeing is still having a hard time with valves (Starliner) and welding (SLS). ULA needs the joint permission of Boeing and Lockmart to buy a box of donuts for engineers. NG won't do rockets unless there is a fuse sticking out the bottom for lighting. ArianeSpace needs to have its plans vetted by the function equivalent of the UN with similar amount of dispensation of favors and kickbacks. Russian rocket folks are more worried about their roofs falling on their heads. BO might do something some day perhaps maybe.

You didn't mention China. They seem to be heavily subsidising the development of the private space industry there and I suspect they will be the third to fly a rocket with a reusable first stage after SpaceX and BO. They may have issues with the metallurgy but presumably they can get Russian companies to make parts if they have to.

Can you imagine any of the other traditional space companies trying this? They would announce a plan in 2012-2013 and today we would be reading about an updated powerpoint that they released showing yet another slightly updated model of how it might look one day, if they get the additional $8.6 billion they NEED to complete.

Isn't this the current Boeing/ULA aproach?

I mean as long as you pay your lobbyists & congresscritters enough, they will deliver taxpayer money, you just have to specify where you want the dump trucks to unload..

I can only imagine that with SLS/Starliner money, SpaceX would be half-way through terraforming Mars by now.

Can anyone enlighten me on how far down the Raptor can throttle - does StarHopper have to slam like the Falcon 9 or can it hover like the New Shepard?

Without knowing the dry mass of the hopper and how much fuel SpaceX put in it, this is impossible to tell. Some educated guesses put the dry mass at ~100 t and the fuel capacity at ~450 t, which would mean it can only be partially filled if they want to lift off work one engine at ~175 t thrust.

I know it's being rather picky, but Ars should be expected to maintain a standard that others can emulate.

"Onto" in this use case is essentially a synonym of on-board. This whole thing is somewhat pedantic, and does not add clarity. For instance reasonable to say "the person drove the car onto the container ship" even if it is deep in the hold, even though the generally accepted onto would be on top of.

Grasshopper tests were really only 6~7 years ago? Wow, today, these propulsive landings have become the normal for SpaceX, just goes to show how fast they actually move.

Can you imagine any of the other traditional space companies trying this?

Boeing is still having a hard time with valves (Starliner) and welding (SLS). ULA needs the joint permission of Boeing and Lockmart to buy a box of donuts for engineers. NG won't do rockets unless there is a fuse sticking out the bottom for lighting. ArianeSpace needs to have its plans vetted by the function equivalent of the UN with similar amount of dispensation of favors and kickbacks. Russian rocket folks are more worried about their roofs falling on their heads. BO might do something some day perhaps maybe.

You didn't mention China. They seem to be heavily subsidising the development of the private space industry there and I suspect they will be the third to fly a rocket with a reusable first stage after SpaceX and BO. They may have issues with the metallurgy but presumably they can get Russian companies to make parts if they have to.

Linkspace a Chinese private launch provider just did their first untethered test of a small grasshopper like vehicle.

The full version looks like a very small Falcon 9. It has a gross mass of 33t and is designed for the small lift market putting 200kg into SSO. If they are successful then they could disrupt the small lift market the way SpaceX disrupted the medium lift market.

We are witnessing a race, it is a race to develop the last expendable rocket. I am not sure who will win it but they won't be happy about it.

Given that Ars is published on the world wide web I wish times were given in GMT/UTC in addition to the US time.

I feel your pain. The local to UTC and UTC to local conversions are straightforward, but a pain in the ass. Worse, though, is that "6 pm ET" is ambiguous, and can refer to either Standard or Daylight Savings time. An accurate conversion requires knowledge of regional specifics, something that is NOT inherently obvious, because the adoption of Daylight Savings time is not universal, and the transition dates are not standard (so to speak).